Speaker
Description
Understanding the mechanisms that govern the turbulent dynamics in tokamak devices is of primary interest for achieving a net production of energy from nuclear fusion processes.
In this work, we investigate the turbulent transport of blob-like structures in the Scrape-Off Layer by means of numerical simulations based on the reduced Braginskii equations in a simplified geometry. We derive a novel third-order exact law for the characterization of the turbulent cascade in electrostatic turbulence.
The dynamics perpendicular to the magnetic field are first investigated using both classical Eulerian analysis and a Lagrangian approach, while varying the ambient plasma conditions. It is found that the radial magnetic gradient and the mean plasma profiles of density and temperature play a crucial role in determining the transport properties. Moreover, by following fluid tracers, diffusive transients in the radial transport are observed at length scales larger than the typical blob size.
Finally, in order to better characterize the cascade process through refined laws, we follow the Yaglom-Monin approach to derive a new third-order turbulence law in increment form for the electrostatic Braginskii model. The validity of the novel Yaglom–Braginskii law is confirmed through high-resolution direct fluid simulations. Specifically, the analysis reveals that the plasma dynamics obey the new cross-scale balance, showing a clear inertial range of turbulence. The new third-order law can accurately measure the cascade rate of density fluctuations at the tokamak edge.
Our results might open a new pathway toward a better understanding of the nonlinear processes in tokamaks, where turbulence plays a major role in plasma confinement.
